Dural arteriovenous fistulas (dAVFs) are abnormal connections between an artery and a vein in the tough covering over the brain or spinal cord (dura mater). Abnormal passageways between arteries and veins (arteriovenous fistulas) may occur in the brain, spinal cord or other areas of your body. Dural AVFs tend to occur later in life, and they're not typically passed on genetically — children aren't more likely to develop a dAVF simply because their parent has Although some dAVFs stem from identifiable causes, it's thought that dAVFs involving large brain veins usually develop due to narrowing or blockage of one of the brain's venous sinuses, which normally route circulated blood from the brain back to the heart.